Question

What is the mass of one mole of magnesium nitrate `Mg(NO_3)_2`?

Answer 1

Got me! I know that 1 mole of magnesium has a mass of 24.3 g.

Explanation:

And I know that 1 mole of nitrogen has a mass of 14.01 g, and that 1 mole of oxygen has a mass of 15.99 g. Do you think that by adding the masses together, appropriately weighted, i.e. `1xxMg + 2xxN + 6xxO`, you would arrive at the formula mass of `Mg(NO_3)_2`?

After you do that, you could see if your summation is right. Good luck.

Answer 2

It is equal to the molecular weight, 147 grams. Use the mole definition.

Explanation:

Mole is defined as:

`n=m/(Mr)`

where:

`m` is the mass in grams.
`Mr` is the molecular weight of the substance.

The molecular weight of a substance is equal to the sum of the molecular weights of the atoms that constitute it. For these atoms:

`Mg:24.3`
`N:14`
`O:16`

So the molecular weight:

`Mg(NO_3)_2=MgN_2O_6`
`Mr=23+2*14+6*16`
`Mr=147`

Therefore:

`n=m/(Mr)`

`m=n*Mr=1*147=147grams`